Aligned brush analogue-to-digital converter



Dec. 25, 1962 c, WALDRQN ET AL 3,070,787

ALIGNED BRUSH ANALOGUE-TO-DIGITAL CONVERTER Filed. Sept. 26, 1958 2 Sheets-Sheet 1 INVENTORS Mime/r7- C. WflLDPO/V Eggs/27- E D/ Mme 14 7'7'ORNE Y Dec. 25, 1962' M. c. WALDRON ETAL 3,070,787

ALIGNED BRUSH ANALOGUE-TODIGITAL CONVERTER Filed Sept. 26, 1958 2 Sheets-Sheet 2 flTTOPA EY United dtates Patent Ofifice 3,976,787 Patented Dec. 25, 1962 3,tl7il,'7ii7 ALIGNED BRUSH AN ALQGUE-TtU-DTGTTAL CJPJVERTER Merritt C. Waldron, Milford, and Robert E. Di Main,

Bridgeport, Conn, assignors to United Aircraft Corporation, East Hartford, Conn, a corporation oi Detaware Filed Sept. 26, 1953, Ser. No. 763,665 6 Jlaims. (Cl. Edd-347) Our invention relates to an analogue-to-digital converter and more particularly to an aligned brush analogueto-digital converter which is more easily set up than are analogue-to-digital converters of the prior art.

The copending application of Jack B. Speller, Serial No. 464,774, filed October 26, 1954, now Patent No. 2,873,440, discloses an analogue-to-digital converter in which respective pairs of brushes engage rows of segments disposed in a coded pattern. The brushes of each pair are spaced by a predetermined distance related to the length of individual segments of the row which they contact. The brushes of each pair are positioned with respect to a reference line on the disk so that as the disk and brushes are driven relative to each other, the converter produces a digital output representing the position of the disk with respect to the brushes. While this arrangement effectively minimizes the possibility of an ambiguity occurring in the output representation of the converter in the manner described in the application, there occurs another problem. The position of each brush with respect to the other brush of a pair and the position of each brush with respect to the reference line must be individually adjusted. This tedious operation must not only be performed when the apparatus is initially set up, but also must be performed when the brushes shift after a period of time in use of the device. If the best result is to be obtained with certainty in the use of this converter, the positions of the brushes must be checked carefully before the converter is used. This checking operation requires individual checking of the positions of all brushes.

We have invented an aligned brush analogue-to-digital converter which eliminates the difiicult setting up operation required in the converter disclosed in the copending application referred to hereinabove. Our converter includes a plurality of brushes, all of which are aligned with respect to each other with the result that the position of all brushes may be set up and checked in a simple, single operation. The construction of our converter is such that only a single brush is required to contact one row of segments with the result that wear of the se ments is reduced.

One object of our invention is to provide an aligned brush analogue-to-digital converter which is more easily set up than are analogue-to-digital converters of the prior art.

Another object of our invention is to provide an aligned brush analogue-to-digital converter, the positions of all brushes of which may be set up and checked in a simple, single operation.

A further object of our invention is to provide an aligned brush analogue-to-digital converter in which Wear of the segments of the individual rows is reduced.

Other and further objects of our invention will appear from the following description.

In general, our invention contemplates the provision of an aligned brush analogue-to-digital converter including a first member carrying a first row and a plurality of pairs of additional rows of conductive segments. The

lengths of the segments of the first pair of rows are double the lengths of the segments of the first row. Similarly the lengths of the segments of the second pair of rows are double the lengths of the segments of the irst pair of rows. We stagger the segments of the respective rows of a pair of rows through a distance equal to half a segment length. A plurality of brushes aligned in a direction transversely of the rows of segments contact the respective rows of segments. We mount the aligned brushes on a second member with respect to which the first member is made moveable. Our converter includes means for deriving outputs from the first row and from succeeding pairs of rows, and means for coupling the outputs from a preceding row to the respective pairs of brushes associated with the succeeding pair of rows. We provide our converter with means for coupling a least significant bit and its complement obtained from the first row to the pair of brushes associated with the first pair of rows to cause the first pair of rows and succeeding pairs of rows to produce bits and complements of a digital representation of the position of the first member with respect to the second member in increasing orders of significance.

in the accompanying drawings which form part of the instance specification and which are to be read in conjunction therewith and in which like reference numerals are used to indicate like parts in the various views:

FIGURE 1 is a plan view of one disk of our aligned brush analogue-to-digital converter showing the relative disposition of the rows of conductive segments and brushes.

FIGURE 2 is a developed view of the segments and brushes of one unit of our aligned brush analogue-todigital converter.

Referrin. now to the drawings, our aligned brush analogue-to-digital converter includes a disk 10 secured to a shaft 12 for rotation with the shaft by any convenient means such as a key 14. Disk 10 carries an input row, indicated generally by the reference character 16, of segments 18 separated by intersegmental spaces 20. We connect the individual segments 18 of the row 16 to a slip ring 22 from which is obtained an output signal as will be described hereinafter.

Our converter includes a plurality of pairs of rows of segments indicated generally by the reference characters 24, 26, and 28. The first pair 24 of rows of segments includes a first row of segments 30 and a second row of segments 32. We connect alternate ones of the segments 39 to a slip ring 34 and connect the other segments 30 to a slip ring 36. We connect alternate ones of the segments 32 to the slip ring 34 and connect the other segments 32 to the slip ring 36.

The pair of rows of segments 26 includes a first row of segments 38, alternate ones of which are connected to a slip ring it and the other segments of which are connected to a slip ring 42. The pair 26 rows of segments includes a second row of segments 44, alternate ones of which are connected to the slip ring 40 and the others of which are connected to the slip ring 42.

The pair 23 includes a first row of segments 46, one segment of which is connected to a slip ring 48 and the other segment of which is connected to a slip ring 50 and a second row of segments 52, one segment of which is connected to slip ring 48 and the other segment of which is connected to slip ring 50.

7e stagger the respective segments of the rows of each pair through a distance of half a segment length. If the segments and intersegmental spaces of the first row 16 have a length L, segments 32 and 3% have an approximate length of 2L, and the length of the segments of the pair of rows 26 and of the pair of rows 28 is substantially doubled from pair to pair. We may mount the rows of segments on the disk 19 in any suitable manner and may make appropriate connections between the segments and the slip rings in any suitable manner known to the art. Preferably, however, we photoetch the segments and slip rings on the disk 16 in such a manner that the slip rings are integrally formed with the segments to which they are connected.

We provide our converter with a plurality of aligned brushes 54, 56, SS, 60, -62, 64, and 66 mounted on a member stationary with respect to the disk 16. Each brush is adapted to engage the segments of the rows of segments 13, 32, 3t 44, 38, 52, and 46, respectively.

We provide our converter with means for applying a least significant bit and its complement to the pair of brushes 56 and 58 associated with the first pair 24 of rows of segments 32 and 31%. We connect a conductor 68 between the positive terminal 76 of a suitable source of potential and the input resistor 72 of a high-gain D.C. inverting amplifier 76 across which a feed-back resistor 74 is connected. We connect the output terminal of amplifier 76 to one input resistor 73 of a high-gain D.C. summing amplifier 80 across which we connect a feed-back resistor 82. We connect a brush 84 adapted to engage slip ring 22 to a conductor 86 connected to a second input resistor 88 of amplifier 8d. The brush 54 associated with the row of segments is connected to the conductor 68. We chose all the resistors 72, 74, 78, 82, and 88 to have equal values. From the structure just described, it will be seen that with brush 54 in engagement with a segment 18, an output appears on the conductor 86. At the same time the potential applied to amplifier 76 through resistor 72 produces an inverted output which in turn is applied to amplifier 80 through resistor 78. At the same time the output on conductor 86 is applied to the input of amplifier Sil through resistor 38. The inverted output of amplifier 76 and the potential of conductor 84 cancel through resistors 73 and 88, with the result that no output appears on a conductor 91) connected to the output terminal of amplifier 8% With brush 54 in an intersegmental space 261 of the row of segments 18, conductor 86 carries no output signal. At this time, however, the inverted output of amplifier 76 is applied to amplifier 80 and no potential appears across resistor 88. Thus amplifier 80 inverts its input signal to produce an output signal on conductor 90. It will be seen that this arrangement causes conductor 86 to carry an output signal when brush 54 engages a segrent 18 while assuring that conductor 90 carries no output at this time. With brush 54 in an intersegmental space 217, conductor 90 carries an output signal while conductor 86 does not. It will be appreciated that conductor 90 carries the least significant bit of the digital representation of the angular position of disk with respect to the brushes, and conductor 86 carries the least significant complement.

Respective diodes or crystals 92 and 94 connect conductors 86 and 90 to brushes 56 and 58 which apply the least significant complement and the least significant bit, respectively, to the rows of segments 32 and 3t). Respective brushes 96 and 98 engage the slip rings 34 and 36 and couple the output signals from the rows of the second pair 24 of rows to a pair of output conductors 100 and 162, to which the brushes 96 and 98 are connected. We connect respective loading resistors 194 and 106 between conductors 100 and 102 and ground. Respective diodes or crystals 168 and 110 connect conductor 102 and 160 to brushes 60 and 62, thereby to couple the next-toleast significant bit and its complement to the pair 26 of rows of segments 44 and 38.

Respective brushes 112 and 114, which engage slip rings 41 and 42, couple the outputs from the pair 26 of rows to respective conductors 116 and 118, to which these A brushes are connected. We connect respective loading resistors 120 and 122 between conductors 116 and 11S and ground. Respective diodes or crystals 124 and 126 conduct the next-to-most significant bit and its complement to brushes 66 and 64 associated with the pair 28 of rows of segments 46 and52.

Respective brushes 128 and 130, which engage slip rings 48 and 5t}, conduct the outputs from the pair 28 of rows of segments 52 and 46 to respective conductors and 134. We connect respective resistors 136 and 138 between conductors 132 and 134 and ground.

The segments and brushes of our converter are constructed and arranged in the manner described hereinabove to cause the output conductors to carry a digital representation and its complement of the angular position of shaft 12 with respect to the stationary brushes. For purposes of clarity, we have indicated the respective relative positions of the brushes and segments by the reference characters X to X With the brushes and segments in the X position, for example, brush 54 does not engage a segment 13 with the result that conductor 86 carries no output signal, thereby representing a 0, while conductor 96 carries an output signal, representing a l in the binary code. In this relative position of the brushes and disk, brush 56 is transferring from a segment 32 associated with slip ring 36 to a segment 32 associated with a slip ring 34. At this time, however, brush 56, connected to conductor 86, carries no output signal, and thus is not required to couple any signal to the row of segments 32. At the same time, brush 53 connected to conductor 99 carries an output signal and engages a segment 30 connected to slip ring 36. From the foregoing, it will be seen that in this relative position of the disk and brushes conductor 102 carries an output signal, representing a 1, while conductor 191) carries no output signal, thereby representing a O.

In the X relative position of the disk and brushes, brush 6t) engages a segment 44 connected to slip ring 40. Since brush 60 connected to conductor 102 carries a signal, brush 112 couples an output signal to conductor 116. At the same time, brush 62, which carries no signal, is just engaging a segment 38 connected to slip ring 40. Thus conductor 116 carries a signal representing a 1, while conductor 118 carries no signal, thereby representing a O.

In the X relative position of the disk and brushes, brush 64, which carries no signal since it is connected to conductor 118, is transferring from a segment 52 associated with slip ring 50 to a segment 52 associated with slip ring 48. At the same time brush 66, which carries a signal since it is connected to conductor 116, is in engagement with the central portion of a segment 46 connected to slip ring 50. Thus conductor 132 carries no signal, thereby representing a 0, while conductor 134 carries a signal representing a 1.

From the foregoing, it will be seen that in the X relative position of the disk and brushes, the conductors 132, 116, 16%, and 90, which may be designated the bit output conductors, respectively represent 0, l, 0, l, which is the desired digital representation of the number 5. At the same time the complement output conductors 134, 118, 162, and 86 respectively represent 1, 0, l, (3, which is the digital representation of the number 10, or the complement of the number 5 in a system representing the counts from O to 15.

The output representations in the remaining relative positions of the disk and brushes may be determined in a manner similar to that outlined hereinabove in connection with the X relative position. We have shown the output" of tr e respective output conductors in all the relative positions of the disk and brushes in Table 1 below.

TABLE 1 Output Conductors Binary Number Binary Comp. Position Dec. Dec.

No. Comp. 132 116 100 90 134 118 102 86 O 0 0 0 1 1 1 1 15 O 0 0 1 1 1 1 1 0 14 0 O 1 0 2 1 1 0 1 13 0 0 1 1 3 1 1 O 0 12 0 1 0 0 4 1 0 1 1 11 0 1 0 1 5 1 0 1 0 0 1 1 0 6 1 0 0 1 9 0 1 1 1 7 1 0 0 0 8 1 0 O 0 8 0 1 1 1 7 1 0 0 1 9 O 1 1 0 G 1 0 1 0 10 0 l O 1 5 1 0 1 1 11 O 1 0 0 4 1 1 0 0 12 0 0 1 1 3 1 1 0 1 13 0 0 1 0 2 1 1 1 0 14 0 0 O 1 1 1 1 1 1 15 0 0 0 0 0 While we have shown a converter having only one disk adapted to divide a circle into 16 parts, it is to be understood that our converter may include a number of disks geared together in a manner more fully described in the copending application referred to hereinabove. Further, we may provide an arrangement of segments which divides a circle into as many parts as is desire-d. We are limited in this respect only by the physical limitations of the disk.

Owing to the symmetry of our converter, we may pr0- vide the converter with auxiliary brushes 140, 14 2, 144i, 1%, 14-5 152, and 158 spaced 180 from and connected to the respective brushes '54, 55, 58, as, 62., 64;, and 66. These auxiliary brushes guard against the possibility of an erroneous output in the event dirt or the like prevents contact between one of the primary brushes and the associated segments. To avoid having a primary brush and its associated auxiliary brush from following the same track on a corresponding row of segments, we may space the primary brush at a slightly different radial distance from the axis of shaft 12 than its auxiliary brush.

In use of our aligned brush analogue-to-digital conver er, we may readily set up the converter merely by aligning all the brushes along a diameter passing through the axis of shaft 12. This can be accomplished in a simple, single operation. Upon movement of shaft 12 relative to the brush supporting member, the respective conductors 132., 116, 106, and 9t) carry the digital representation of the relative position of the disk with respect to the brush supporting member in accordance with Table 1 hereinabove. At the same time the conductors 134, 118, 1&2, and 85 carry the complement of the number representing the relative position of the brushes and disk. The setting of the brushes may readily be checked at any time during the use of the device merely by assuring that all brushes are aligned along a diameter. If desired, auxiliary brushes may be employed to avoid the danger of an erroneous output in the event dirt prevents contact between a primary brush and the segments of its associated row.

In the linear form of our converter as shown, the lengths of the segments double from row to row; but it will beappreciated that for a nonlinear converter this simple relationship will no longer exist. It can be seen in FIGURE 2 that the segment 32 contacted by brush 56 in the position shown subtends a length of arc substantially equal to half the X interval plus the entire X interval plus half the X interval; and the ends of this segment 32 are aligned substantially with the midpoints or" the X and X intervals, respectively. This segment 32 engaged in the position shown by brush 56 overlaps and contacts within the region of overlap a segment 36 and this segment 31 subtends a length of are substantially equal to half the X interval plus the entire X interval plus half the X interval; and the ends of this segment 3d are aligned substantially with the midpoints of the X and X intervals, respectively; and these segments 32 and 3t} overlap through substantially half the X interval plus half the X interval. These two overlapping segments 30 and 32 may be termed auxiliary segments. It will further be seen that the segment 32 associated with the dimension 2L subtends a length of are substantially equal to half the X interval plus the entire X interval plus half the X interval; and the ends of this segment 32 are aligned substantially with the midpoints of the X and X intervals, respectively. This segment 32 associated with the dimension 2L overlaps and contacts within the region of overlap a segment 3%; and the segment 3i subtends a length of arc substantially equal to half the X interval plus the entire X interval plus half the X interval; and the ends of this segment 30 are aligned substantially with the midpoints of the X and X intervals, respectively; and these segments 32 and 3t) overlap through substantially half the X interval plus half the X interval. These segments 3t) and 32 associated with the dimension 2L may be termed primary segments. Finally it will be seen that the primary segment 32 associated with the dimension 2L overlaps the auxiliary segment 3% through substantially halt the X interval plus half the X interval. For nonlinear counts the lengths of segments of our converter will not be precisely the same as in converters of the prior art' In converters of the prior art the lengths of segments are such that the ends thereof substantially coincide with transfer points between intervals. In our converter the lengths of segments are such that the ends thereof substantially coincide with rnidpoints of the intervals.

It will be seen that we have accomplished the objects of our invention. We have provided an aligned brush analogue-to-digital converter which may be set up more rapidly and expeditiously than is possible with analogueto digital converters of the prior art. The positions of the brushes may be set up and checked in a simple, single operation. If desired, our converter may be provided with auxiliary brushes for preventing erroneous outputs resulting from dirt preventing contact between a primary brush and its associated segments.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of our claims. it is further obvious that various changes may be made in details within the scope of our claims without departing from the spirit of our invention. It is, therefore, to be understood that our invention is not to be limited to the specific details shown and described.

Having thus described our invention, what we claim is:

1. An analogue-to-digital converter disk including in combination a first circle comprising a first and a second and a third electrically conductive segment spaced apart to define a first non-conductive space between the first and second segments and a second non-conductive space between the second and third segments with the first segment subtending a first central angle and the second segment subtending a second central angle and the first space subtending a third central angle and the second space subtending a fourth central angle and the third segment subtending a fifth central angle, a second circle comprising a primary conductive segment subtending a central angle substantially equal to the third central angle plus half the sum of the first and second central angles and an auxiliary conductive segment subtending a central angle substantially equal to at least the aggregate of the fourth central angle and half the sum of the second and fifth central angles, a third circle comprising a primary conductive segment subtending a central angle substantially equal to the second central angle plus half the sum of the third and fourth central angles and an auxiliary conductive segment subtending a central angle appreciably greater than the sum of the fifth central angle and half the fourth 7 central angle and means mounting said segments on said disk with said circles in concentric relationship and having different respective radii with the segments of the second and the third circles mounted such that the auxiliary segments thereof overlap through a central angle substantially equal to one half the sum of the fourth and fifth central angles.

2. An analogue-to-digital converter disk including in combination a first circle comprising a first and a second and a third electrically conductive segment spaced apart to define a first non-conductive space between the first and second segments and a second non-conductive space between the second and third segments with the first segment subtending a first central angle and the second segment subtending a second central angle and the first space subtending a third central angle and the second space subtending a fourth central angle and the third segment subtending a fifth central angle, a second circle comprising a primary conductive segment subtending a central angle substantially equal to the third central angle plus half the sum of the first and second central angles and an auxiliary conductive segment subtending a central angle substantially equal to at least the aggregate of the fourth central angle and half the sum of the second and fifth central angles, a third circle comprising a primary conductive segment subtending a central angle substantially equal to the second central angle plus half the sum of the third and fourth central angles and an auxiliary conductive segment subtending a central angle appreciably greater than the sum of the fifth central angle and half the fourth central angle and means mounting said segments on said disk with said circles in concentric relationship and having different respective radii with the segments of the second and third circles mounted such that the auxiliary segments thereof overlap and contact each other through a central angle substantially equal to one half the sum of the fourth and fifth central angles.

3. An analogue-to-digital converter disk including in combination a first circle comprising a first and a second and a third electrically conductive segment spaced apart to define a first non-conductive space between the first and second segments and a second non-conductive space between the second and third segments with the first segment subtending a first central angle and the second segment subtending a second central angle and the first space subtending a third central angle and the second space subtending a fourth central angle and third segment subtending a fifth central angle, a second circle comprising a primary conductive segment subtending a central angle substantially equal to the third central angle plus half the sum of the first and second central angles and an auxiliary conductive segment subtending a central angle substantially equal to at least the aggregate of the fourth central angle and half the sum of the second and fifth central angles, a third circle comprising a primary conductive segment subtending a central angle substantially equal to the second central angle plus half the sum of the third and fourth central angles and an auxiliary con ductive segment subtending a central angle appreciably greater than the sum of the fifth central angle and half the fourth central angle and means mounting said segments on said disk with said circles in concentric relationship and having different respective radii with the segments of the second and third circles mounted such that the auxiliary segments thereof overlap and contact each other through a central angle substantially equal to one half the sum of the fourth and fifth central angles, and such that the primary segment of the third circle overlaps the auxiliary segment of the second segment through a central angle substantially equal to one half the sum of the second and fourth central angles.

4. In an analogue-to-digital converter a disk, a first circle of conductive segments, a second circle of conductive segments, said segments of said circles being all of the same length, means mounting the segments of said circles on said disk with each segment of said first circle overlapping a pair of the segments of said second circle such that respective segments of the first circle each contacts one segment of the second circle at points in the region of overlap, a first conductive ring, means mounting said first conductive ring on said disk such that it contacts alternate segments of said first circle, a second conductive ring; and means mounting said second conductive ring on said disk such that it contacts segments of said second circle which contact segments of the first circle other than said alternate segments of the first circle.

5. An analogue-to-digital converter including in combination a disk, a plurality of successive pairs of circles of conductive segments, the segments of each pair of circles having the same length, means mounting the segments of said circles on said disk with each segment of one circle of each pair overlapping a pair of segments of the other circle of the pair such that respective segments of the one circle each contacts one segment of the other circle at points in the region of overlapping, means for producing a pair of complementary inputs, means for applying said inputs respectively to the segments of the circles of the first one of said pairs, means for deriving complementary outputs from the segments of the circles of said pairs and means comprising a pair of brushes spaced along a radius of said circles for applying the complementary outputs of the segments of a pair respectively to the segments of the circles of a succeeding pair.

6. An analogue-to-digital converter including a disk carrying a first circle comprising a first and a second and a third electrically conductive segment spaced apart to define a first non-conductive space between the first and second segments and a second non-conductive space between the second and third segments with the first segment subtending a first central angle and the second segment subtending a second central angle and the first space subtending a third central angle and the second space subtending a fourth central angle, a first conductive ring contacting the segments of the first circle, a second circle comprising a primary conductive segment subtending a central angle substantially equal to the third central angle plus half the sum of the first and second central angles and a third circle comprising a primary conductive segment subtending a central angle substantially equal to the second central angle plus half the sum of the third and fourth central angles, means mounting said segments on said disk with said circles concentrically disposed, said circles having different respective radii, the segments of the second and third circles overlapping through a central angle substantially equal to half the sum of the second and third central angles and contacting one another at a point in the region of overlap, a second conductive ring contacting the segment of one of the second and third circles, a coupling device for the second circle, a coupling device for the third circle, means mounting said coupling devices in coupling relationship with their associated circles and with said coupling devices radially aligned and a respective coupling device for each of the first and second conductive rings.

References Cited in the file of this patent UNITED STATES PATENTS 2,620,980 Brown Dec. 9, 1952 2,779,539 Darlington Jan. 29, 1957 2,783,464 Canepa Feb. 26, 1957 2,792,174 Rutter May 14, 1957 2,792,545 Kamm May 14, 1957 2,793.807 Yaeger May 28, 1957 2,818,557 Sink Dec. 31, 1957 2,823,345 Ragland Feb. 11, 1958 2,852,764 Frothingham Sept. 16, 1958 2. 0 Speller Feb. 10, 1959 2,880,410 Postman Mar. 31, 1959 2,907,020 Champion Sept. 29, 1959 

